Positive electrolytic time delay switching mechanism



Jan. 18, 1966 T. K. c. HARDr-:sTY 3,230,326

POSITIVE ELECTROLYTIC TIME DELAY SWITCHING MEGHANISM Filed July 3l, 1964 AGENT.

United States Patent G 3,230,326 POSITIVE ELECTRLYTIC TIME DELAY SWITCHING MECHANISM Thomas K. C. Hardesty, Ednor, Md., assgnor to the United States of America as represented by the Secretary of the Navy Filed .luly 31, 1964, Ser. No. 386,804 1 Claim. (Cl. Zim-61.05) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to time relay switch mechanisms in which the delay is accomplished by electrolytic means, and more particulraly to an electrolytic time delayactuated switching contact system which will positively hold an electrical circuit open until closure is desired and thereafter positively hold the circuit closed with a minimum of contact resistance.

In accordance with this invention, there is provided an electrolytic interval timer in which a spring-biased plunger is restrained by means of an electrolytically-erodable anode element and which, in response to an electric current set up within the electrolyte by the operative connection of the cathode and anoed elements of the timer to a source of electric potential, will incur suicient erosion of the anode element disposed within the electrolyte to release the plunger after a predetermined period of time and allow it to move forward under the action of the spring. Prior to the release of the plunger the switching contacts of an electrical circuit are physically held apart by a non-conductive separator which is an integral part of the plunger itself, and subsequent to the actuation of the electrolytic interval timer and the resultant forward movement of the plunger the switching contacts are engaged by a substantially heart-shaped slot in the plunger which causes them to be wedged together in rm electrical contact. The electrolytic time delay-actuated switching contact system of the present invention is adapted for use in a control circuit to assure maximum reliability in the positiveness of the open and closed positions, and is particularly adapted for use with a marine mine such, for example, as the type launched from a submarine or surface vessel to delay the arming of the mine for a predetermined period of time after the mine has been planted in a body of water.

In devices heretofore proposed for arming a mine, is has been the general practice to employ various time delay mechanisms, including even electrolytic timer devices. Electrolytic timers previously used, however, were dependent upon an air gap and the mere spring force of contact isprings to assure that an electrical arming circuit remained open for keeping the weapon in an unarmed condition until otherwise desired. These devices therefore have not proven to be entirely adequate for use with arming devices for explosive weapons since they have a number of disadvantages such, for example, as fragility, an absence of reliable means for providing av positive open position for the contacts and insuring positive closure of the contacts at appropriate times, and difficulty in the making of wiring connections.

It is therefore an object of the present invention to provide an electrical switching device which will positively hold an electrical circuit open until closure isl desired vand thereafter positively hold the circuit closed with a Aminimum of contact resistance.

Another object of this invention is to provide a new and improved device for positively controlling an elec- ICS trical circuit in which the circuit control is delayed by electrolytic action.

A further object of the present invention is to provide an electrolytic time delay-actuated switching contact system for use in a control circuit to assure maximum reliability in the positiveness of open and closed positions for a switch in the circuit.

Still another object of this invention is to provide a new and improved electrolytic time delay-actuated switching device for use in an electrical arming control circuit of a marine mine or the like which will assure maximum reliability in positively lholding the circuit open until actuated, and thereafter positively hold the circuit closed.

A still further object is the provision of a new and improved electrolytically controlled switch which is simple in construction, economical to manufacture, positive in action and which possesses all of the qualities of reliability and durability in service.

Still other objects and advantages of the invention will become apparent form a consideration of the following detailed description when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a longitudinal cross-section through a switching device formed in accordance with the teachings of the present invention;

FIG. 2 is an end view of the device shown in FIG. l; and

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 1.

Referring now to the drawings on which like numerals of reference are employed to designate like parts throughout the several views and more particularly to FIG. l thereof, there is shown thereon an electrolytic switch indicated generally by the numeral 10 compising an elongated support structure 11, a plastic housing 12 dening a substantially cylindrical-shaped chamber 13 positioned within a central bore 14 of the support structure and containing therein an electrolyte solution suitable for the purpose such as, for example, silver lluoborate, an enlarged head portion 15 of an anode element 16 supported by an inward-protruding portion 7 in the forward end of housing 12 and a cathode element 18 threadably engaging and extending through an end closure member 19 in the rear end of the housing, and a pair of dualized contacts 20. An anode and cathode made of silver has been found suitable, but it is to be understood that other materials might also serve the purpose. The protrusion or plunger housing 17 is provided with a central bore 21 which opens through an apex end 22 thereof, and with counterbores 23, 24 and 25, which serve to support various elements as will appear hereinafter. In this case the term counterbores is not meant to include only a machined structure, as the designated shape could clearly be produced equally as well by molding.

The plunger assembly is indicated generally by the numeral 26 and comprises a main head portion 27, a secondary piston head 28 separated from the main head portion by an annular groove 29 in the body thereof, and a piston rod or tail portion 30, all composed of a suitable non-conductive material such as, for example, a plastic. The anode element 16 is comprised of an elongated wire terminating at one end in an enlarged head portion 15 as aforedescribed and extending therefrom through the bore 21 in the apex end 22 of plunger housing 17, through a central bore 31 which passes through the tail portion 30 and piston head 28, and out slot 32 in the plunger body to annular groove 29 where it terminates as a winding therein Xing it to the plunger.

An O-ring 33 is disposed in counterbore 24 to provide a iluid seal between the anode wire 16 and the protruding portion or plunger housing 17. A washer 34 rests against the step between counterbores 24 and 25, serving to hold O-ring 33 in place and also serving to provide a support for the inner end of a coil spring 35 which acts between the washer 34 and the rear end 36 of a reduced portion of piston head 28 to urge the plunger assembly forwardly.

Connected to the support structure 11 on fiat upper and lower surface areas 37 and 38, respectively, by any suitable means such as, for example, the illustrated screws, are flat plate members 4t) and 40' formed of a suitable conductive material, each being provided at one end with an upstanding terminal lug 41 facilitating connection into an electrical circuit and at the other end with a pair of integral spring lingers 42 extending along the support surface in spaced relation and bent inwardly at a slotted portion 43 provided in the support structure at the forward end thereof, and terminating in the aforedescribed contact surfaces 20 wrapped about contact pins 44.

The main -head portion 27 of the plunger assembly 26 includes a disc element 45, an elongated flat element 46 fixed at one end to the disc in perpendicular relationship with both the disc and the flat upper and lower surfaces 37 and 38 of support 11, and a contact separator member 47 mounted at the other end of the element 46 perpendicular to both the disc and the elongated element and parallel with the flat upper and lower surfaces 37 and 38, the latter serving to maintain separation of the contact surfaces 20 until the device is actuated. A substantially -heart-shaped slot 48 is provided in the elongated element 46 with the lobes thereof positioned in the forward region of element 46 adjacent contact separator 47 and the apex rearward thereof, providing means in the element 46 for passage therethrough yof the contact pins 44. In the normal disposition of the various elements then, the spring fingers 42 are bent inwardly in slot 43 on either side of elongated member 46, the spring Contact surfaces 20 of the upper pair being` separated from the contact surfaces 20 of the lower pair by Contact separator 47, thus maintaining the electrical circuit in the open position. When the plunger assembly is actuated, however, it i's moved forward under the action of spring 35, moving contact separator 47 away from contact surfaces 20, and engaging the contact pins 44 with the apex portion of the heart-shaped slot 48 to thereby draw spring lingers 42 iiat against surfaces 37 and 38 and wedge the upper and lower contact surfaces 20 together in firm electrical contact.

Electrical connection is made to the anode by means of an anode contactor plate 49, best illustrated in FIG. 2, which is secured to one side of the support 11 and is provided with a resilient linger portion which is bent at a right angle to lit into annular groove 29 where it contacts the wound anode wire 16. An upstanding terminal lug 41 is provided on the contactor plate 49 for the purpose yof facilitating connection into suitable control circuitry, not shown.

Completing the electrolytic cell is the cathode element 18 having a terminal 41 thereon to which a lead from the above-mentioned control circuitry may be attached. It should be noted that it is desirable not to completely ill the chamber 13 with electrolyte so as to leave an air bubble 50 in the chamber to allow for expansion and contraction of the electrolyte during temperature changes. It is contemplated that the present switch may be used in areas where the temperature may fall low enough to freeze the electrolyte and the presence of the air bubble insures that the housing will not be ruptured in this event. The particular construction of the plunger housing 17, placing the anode head at the end of a portion protruding into the chamber 13, has been adopted to insure that bubble 50 will not surround the anode head 15 should the device be placed in a position in which the anode head is uppermost in the chamber. The device would obviously be inoperative if the anode were not completely immersed in the electrolyte.

In the operation of the switch of the present invention the size of anode head 15 and the current to be passed through the electrolyte are first predetermined in order to establish a desired delay time for switch actuation. When it is desired to start the device, the control circuit is closed to supply the predetermined current to the cell. Electrolytic erosion of the anode head 15 then takes place until the size of the head is reduced sufficiently to remove the restraint on the spring-biased plunger. At that time the plunger moves forwand to actuate the switch, Wedging the contact surfaces 20 together in firm electrical contact.

It should be readily apparent that an electrolytic time delay-actuated switching Contact system is provided by the present invention having positive open and closed positions, which are assured by the unique plunger head construction'incorporating a Contact separator to keep the contacts separated prior to actuation and a heart-shaped slot to wedge the contact surfaces firmly together after actuation. The dualized contacts assure low contact resistance and high current carrying capacity. The closure rate of the contacts will minimize arcing and the wedging action reduces the possibility of contact bounce and provides good contact signature.

From the foregoing it will be readily apparent that the present invention provides numerous advantages not to be found in prior art devices. Although the invention has been described in connection with a preferred embodiment, it is to be understood that other arrangements may be devised by those skilled in the art to achieve similar embodiments which incorporate the principles of the present invention and fall within the spirit and scope thereof.

What is claimed is:

A positive electrolytic time delay switching mechanism comprising:

a substantially cylindrical housing composed of a plastic material and having a well portion formed in one end thereof with a bore in the base of said well opening into the housing,

said housing being further provided with a pair of external flat surfaces on diametrically opposed portions of the peripheral wall thereof,

a rod-shaped anode member in said bore having an enlarged head portion thereon disposed within the housing,

means closing the other end of said housing and including a cathode member extending therethrough,

a silver fluoborate electrolyte solution in said housing, said housing being incompletely filled therewith so as to leave an air bubble therein,

a plastic plunger attached to the rod portion of said anode member and disposed Without said housing substantially closing said well portion of the housing,

a coil spring positioned within said well portion and acting between the plunger and the base of said well portion for urging said plunger outward from said well portion, outward motion of said plunger being normally prevented by engagement of said enlarged head portion of the anode with the base of said well portion within the housing,

conductive plate means secured to each of said ilat surfaces of said housing, each plate having a pair of integral spring arms extending along said flat surface and being bent inwardly over the end surface yof said housing,

contact pins secured to each of said spring arms, said spring arms of one plate urging said pins thereof into contacting relationship with the pins of the arms of the other plate,

said plunger being provided with a contact separator for normally maintaining said contact pins in an initial spaced position and further having a substantially heart-shaped slot therein for receiving the contact pins in the lobe portion thereof,

whereby when an electric current is passed through said electrolyte, the enlarged head portion of said anode is eroded until it is small enough to pass through said bore, whereupon said plunger is moved outward by said spring, moving the contact separator thereon out of engagement with said contact pins and causing the Icontact pins to be wedged together in the apex of said heart-shaped slot in rm electrical contact.

References Cited by the Examiner UNITED STATES PATENTS Kissinger et al. 200-33 X McWilliams 200-153 Carlson et al. 200-67 Lyon 200-61 BERNARD A. GILHEANY, Primary Examiner.

R. N. ENVALL, JR., Assistant Examiner. 

